Portable chair insert for back support



FIG. 1 is a perspective view of the front side of a portable chair insert for back support in the open position showing my new design;

FIG. 2 is a perspective view of the back side of the portable chair insert for back support of FIG. 1;

FIG. 3 is a perspective view of the front side of the portable chair insert for back support of FIG. 1 in the closed position; and

FIG. 4 is a perspective view of the back side of the portable chair insert for back support of FIG. 1 in the closed position. 

The ornamental design for portable chair insert for back support, substantially as shown. 